Egyptians security forces escort an Islamist supporter of the Muslim Brotherhood out of the al-Fatah mosque and through angry crowds, after hundreds of Islamist protesters barricaded themselves inside the mosque overnight, following a day of fierce street battles that left scores of people dead, near Ramses Square in downtown Cairo, Egypt, Saturday, Aug. 17, 2013. Authorities say police in Cairo are negotiating with people barricaded in a mosque and promising them safe passage if they leave. Muslim Brotherhood supporters of Egypt’s ousted Islamist president are vowing to defy a state of emergency with new protests today, adding to the tension.

CAIRO — Egyptian security forces stormed a Cairo mosque Saturday after a heavy exchange of gunfire with armed men shooting down from a minaret, rounding up hundreds of supporters of the country’s ousted president who had sought refuge there overnight after 173 people died in violent clashes.

The raid on the al-Fath mosque on Ramses Square was prompted by fears that deposed President Mohammed Morsi’s group, the Muslim Brotherhood, again planned to set up a sit-in, security officials said, similar to those that were broken up Wednesday in assaults that killed hundreds of people.

The arrest of the brother of al-Qaeda chief Ayman al-Zawahri came in connection with the raid on the mosque. Officials said that he planned to bring in armed groups to provide support to those holed up inside the mosque.

Mohammed al-Zawahri, a Morsi ally, is the leader of the ultraconservative Jihadi Salafi group, which espouses al-Qaeda’s hardline ideology. He was detained at a checkpoint in Giza, the city across the Nile from Cairo, the official said.

The official spoke on condition of anonymity because he wasn’t authorized to brief journalists about the arrest.

The Egyptian government meanwhile announced it had begun deliberations on whether to ban the Brotherhood, a long-outlawed organization that swept to power in the country’s first democratic elections a year ago.

Such a ban, which authorities say is rooted in the group’s use of violence, would be a repeat to the decades-long power struggle between the state and the Brotherhood.

For more than a month since the July 3 military overthrow of Morsi, Brotherhood members and supporters have attacked and torched police stations and churches in retaliation. Shops and houses of Christians have been targeted.

Such attacks spurred public anger against the Brotherhood, giving the military-backed government popular backing to step up its campaign against the Islamist group.

The unrest in Egypt has raised international concerns over the country’s stability and prompted U.N. Secretary General Ban Ki-Moon to condemn in a statement Saturday both “violent protests” in reference to Brotherhood’s rallies and the authorities’ “excessive use of force.”

Ban also noted, in an apparent rebuff of Brotherhood demands to reinstate Morsi, that the “political clocks move only forward, not backward.”

Former President Jimmy Carter also expressed concern over the violence, saying it is “rapidly eroding the chances for dialogue and a road to reconciliation.”

In Cairo, the assault on the al-Fath mosque began Friday when pro-Morsi protesters and armed men fled into the worship center to avoid vigilantes and arrest. They piled furniture in the mosque’s entrance to block authorities from reaching them.

By midday Saturday, gunmen took over a mosque minaret and opened fire on the security forces below, the state-run MENA news agency said. The crowd around the mosque panicked as soldiers opened fire with assault rifles.

More in News

The Denver Art Museum plans to funnel a $25 million one-time gift into the estimated $150 million budget for renovating its iconic North Building in time for the structure’s 50th anniversary in 2021, officials announced Thursday.

President-elect Donald Trump is expected to name fast-food executive Andrew Puzder, a vocal critic of substantially increasing the minimum wage and an opponent of rules that would make more workers eligible for overtime pay, as head of the Labor Department.